Multifunctional films with superior mechanical performance, transparency, antibacterial properties enabled by a physical and chemical dual crosslinking network construction

Exploring sustainable and bio-degradable alternative materials based on lignin and cellulose is expected to address the serious environmental problems caused by the continuous accumulation of petroleum plastic waste. One open question is how to make a high mechanical strength lignin-cellulose material without optical haze. Herein, a multifunctional lignin-cellulose film with excellent mechanical properties and high transparency is successfully prepared based on Schiff base chemistry along with multiple hydrogen bonding interactions. Combined with the chemical and physical double cross-linking network, positively charged aminated lignin improves the compatibility with dialdehyde cellulose and also optimizes the internal structure of the material. Significantly, the obtained films (ALDC10) deliver exceptional mechanical properties (tensile strength, 164.8 MPa and Young's modulus, 12.1 GPa), which are higher than those of some commercial petroleum-based plastics. The films endow superior transparency, antimicrobial (>50 %), UV shielding, and water vapor barrier properties, making them suitable for plastics replacement in active food (apple) packaging. Additionally, the transparent films show photothermal conversion properties, which have high potential applications in food vending machine to delay spoilage of foods with reduced energy consumption. This work establishes advanced valorization of cellulose and lignin, with superior performance, which is expected to replace petroleum plastics in various applications.